Raspberry PI - Model A+ 512 MB RAM, 1 USB port, HDMI, Audio output

The Model A+ is the low-cost variant of the Raspberry Pi.
The Raspberry Pi Model A+ is a tiny computer board that's up and running when a keyboard, mouse, display, PSU and MicroSD card with installed OS are added. It’s a miniature ARM-based PC which can run many of the applications that normally require a desktop PC, like spreadsheets, word-processing and games. It also plays High-Definition video. The model A+ features lower power consumption, better audio performance and a 40-pin GPIO connector amongst other improvements over the earlier model A. It is also even smaller! Raspberry Pi is an Open-Source product designed to be supported by Internet-based user forums. As a starting point refer to the Official website at: http://www.raspberrypi.org/.

Note: As of August 10th, 2016 the Raspberry Pi A+ now includes 512 MB of RAM!

The Raspberry Pi Model A+ is the perfect board for the minimalist Pi fan. This low-cost Pi uses the same processor as the model B+, but does away with the Ethernet jack and three of the USB Ports. This makes it lower power, less expensive and much lighter & smaller! It's still compatible with all Pi operating systems and software, and has the exact same 40 pin GPIO connector and camera/display sockets, so any HATs or Pi Plates or other things that plug into the model B+ will work just the same.

It also has the same HDMI, sound/composite connector and microUSB connector for power

Unlike the Raspberry Model B+, there's only one USB port and no ethernet jack but it's also significantly smaller at 65mm x 56mm if you don't include overhang from the connectors.

Don't forget, you'll need a USB power supply with microUSB cable, and a microSD card with a Raspberry Pi OS on it (we suggest a Raspbian 4G card or NooBS 8G card)

We recommend the Model A+ for for embedded projects and projects which require very low power, and which do not require Ethernet or multiple USB ports.

Firmware now looks for add-on boards that comply with the HAT (Hardware Attached on Top) design rules. This allows the Raspberry Pi A+ to set up the GPIO and load drivers to suit an expansion board automatically.

For more information see: http://www.raspberrypi.org/introducing-raspberry-pi-hats/